Sounds like you're on the right track to me. Did you happen to check out Mark & Viola's Jive variation on Ballroomdancers.com a few weeks back? That's a very good example of rock steps in Jive.

Terminology-wise, it's my personal observation that a "rock step" tends to describe a transfer of weight from one foot to the other and back, while a "break" describes an actual stop and/or change of directional movement.

To put it in another way, a back break would imply that you are actually moving backwards and then forward, as in Cha Cha, such that you would transfer all of your weight fully over the whole foot before moving away. By definition, a back rock does not imply direction of movement, but only positions of the feet. So your your body does not have to move backwards when your weight shifts to the back foot.

According to this definition, a break would be a type of rock step, but not vice-versa.